Garmin cadence sensor 2 connected, but not working

Hi all,

I’ve been having some trouble with my Garmin cadence sensor 2 and I hope you can help.

My current setup is a dumb trainer with the garmin speed 2 and cadence 2 sensors, and zwift on an iPhone 8+ which is updated to the most resent iOS. This set up has had no issues, with my last successful ride being 4 days ago (30th of august).

Unfortunately, yesterday and today my training sessions turned into troubleshooting sessions as my cadence sensor would connect to zwift, but wouldn’t register any movement (rpm stayed at 0 despite peddling). My speed would fluctuate as the back wheel spun, but nothing from the pedals.

When trying to connect the sensors, I’ll open the ‘speed sensor’ window, and as soon as the speed sensor is registered, it automatically selects the speed sensor and assigns it to both the speed and cadence sensors. I then manually select ‘cadence sensor’ and select the cadence sensor.

I feel like I’ve tried it all. The batteries are ok and when connected to my Garmin watch, they work fine (was registering cadence); I’ve tried turning my phone off and on again, as well as reinstalling the app; I’ve tried using them while the speed and cadence sensors were paired as Bluetooth devises on my phone, and then forgotten; I’ve tried using them while registered and unregistered on the Garmin app; there’s no significant electromagnetic disruptions around my setup; and in desperation, I even tried assigning the speed sensor as my cadence sensor.

When connecting the sensors to my wife’s phone, they connected just fine and was registering cadence:


The process to connect the sensors was identical to when using my phone. Interestingly I noticed that the cadence sensor seems to have a different number at the end of its serial number (176 instead of 92). Why might this be the case?

If you have any insight as to what the problem might be, I’d be greatly appreciative.

Regards,
Ben

Hi @Ben_Rankin welcome to Zwift forums.

Shuji at Zwift HQ here. It sounds like you’ve already done some of the logical troubleshooting steps. In reading your descriptions - the thing to watch out for during your troubleshooting is diverted pairing.

IIRC, the Garmin version 2 sensors can multi-cast over Bluetooth - meaning they are capable of pairing to more than one receiver (i.e. your wife’s phone, your phone / your Garmin watch). I might be mistaken about the multicast capability, but just because the sensors can multicast, doesn’t mean it plays nicely with Zwift. From the Zwift side of things, we want those sensor signals all to ourselves.

Please also be sure that they’re not paired to the Garmin Connect app on your phone or laptop if you have that installed. The GC app is a known hijacker of signals. For troubleshooting purposes, you may want to uninstall the Garmin Connect app from your smartphone and laptop.

#2 - what’s the LED light on your sensors doing? Per this Garmin support page

If the battery levels look good, you may want to reset the sensor. Again from that Garmin support page:

Once you’ve done all that - are results more stable?